Non-metallurgical grades of alumina have in recent years attained considerable importance as commercial items. These materials have found application in rapidly expanding industries as, for instance, refractory brick, anti-skid surfacing, high-strength porcelain, abrasives, cement catalysts, fire-retardents, high voltage and spark plug insulators, electronics, vacuum tube envelopes, the lighting industry etc.
This invention relates to the production of alumina and, more particularly, to the production of a novel form of alumina having desirable properties rendering it eminently satisfactory for use in producing high alumina, low soda ceramic products and other things.
Currently, synthetic alumina is generally produced from the calcination of aluminum trihydrate which has been derived from bauxite. The product obtained usually contains considerable proportions of soda. The presence of soda is a disadvantage; for example, high electrical insulators prepared from these calcined aluminas have a tendency to lessen their electrical resistance, and it also has an interaction with catalytic castings. Further processing is necessary to reduce the soda content of the alumina. This is just but one of the causes of the uneconomical burden placed on the specialty alumina industry.
Due to their rapid rise in price, the demand for high grade ores, on which many current chemical industries are based, is fast disappearing. The alumina industries are illustrative of such a situation wherein the USA depends on foreign sources for more than 90% of its high grade bauxite. Toth Aluminum Corporation (a U.S. Corporation) has made major thrusts towards the development of economically feasible processes which utilize abundant low-grade ores.
The chlorination of kaolinitic clay, a low grade ore containing in its raw state up to 21% of aluminum metal values, produces a crude aluminum chloride, that after purification, offers a potentially economically feasible means from which specialty aluminas can be obtained via an unique oxidation process.
The instant invention is primarily concerned with the oxidation of high-purity aluminum chloride to make high purity aluminum oxides. More specifically, aluminum oxide of the purity needed to compete in the rapid development of the technologies in the electronic, telecommunication, instrument, lighting, chemical and mechanical industries.